The invention relates to a tomographic apparatus for the production of transverse tomographic images of a radiographic subject, comprising a radiation measuring arrangement including a radiation source which produces a fan-shaped beam of rays penetrating the exposure subject, and whose cross-sectional extent, perpendicular to the layer plane, is equal to the layer thickness, and which is of such a magnitude in the layer plane that the entire exposure subject is permeated, as well as including a radiation receiver which determines the radiation intensity behind the subject, as well as comprising a drive mechanism for the measuring arrangement for producing rotational movements, and comprising a measured value converter for the transformation of the signals supplied by the radiation receiver into a tomographic image, wherein the radiation receiver consists of a number of individual detectors.
A tomographic apparatus of this type is e.g. described in the U.S. Pat. No. 3,778,614. In this tomographic apparatus, a rotation of the measuring arrangement through an angle of approximately 360 degrees is prudent for the purpose of producing the input signals of the measured valve converter. What is disadvantageous in the case of the known tomographic apparatus is that not only the primary radiation issuing directly from the radiation source, but also scatter radiation emitted from the exposure subject acts upon the radiation receiver. This stray radiation also produces output signals from the radiation receiver, so that the output signal of a detector of the radiation receiver is made up of a component originating from the primary radiation and representing the attenuation of the radiation through the exposure subject, and a component originating from the stray radiation which is undesired because it invalidates the tomographic image constructed by the measured value converter.